Michael Trew writes:
On 3/21/2021 7:22 PM, DerbyDad03 wrote:

Another person told me no, I need to have both hots on touching breakers
- opposing phases - because if I don't I can theoretically overload the
neutral line up to 30 AMP if the both circuits are loaded.

This. If they're on opposite phases, the current in the grounded
conductor (aka neutral) approaches zero as the load on each leg
approaches capacity.

If they're on the same phase, the current through the grounded
conductor may be 2x the circuit ampacity.